1. Field of the Invention
The invention concerns a single-ended dc-to-dc converter and, in particular, a single-ended dc-to-dc converter for the pulse control of the voltage at an inductive load. 2. Description of the Prior Art
A single-ended dc-to-dc converter of the transformer type in use today typically comprises: a primary winding which is connected to a d-c voltage source via a switch; a secondary winding which is connected, via a series valve and a choke, to a load with which a by-pass valve is associated; and a magnetization reversal winding which is connected to the d-c voltage source via a limiting resistor in such a manner that the magnetization reversing current flowing in the magnetization reversal winding magnetizes the magnetic core of the transformer in a direction opposite that of the primary current in the primary winding.
Such a prior art dc-to-dc converter is used to convert a fixed d-c supply voltage into a d-c output voltage of variable magnitude (German Auslegeschrift 1,267,322). Moreover, the switch used in such a prior art converter is typically a controlled valve, particularly a thyristor (SCR), included in a d-c control element, while the by-pass valve employed therein is usually an uncontrolled diode, the latter generally being shunted directly across the load.
If in such a single-ended dc-to-dc converter a d-c element is, in fact, used as the switch, the quenching capacitor of the control element is recharged by means of the energy which is stored in the inductances between the d-c control element and the bypass valve. Such recharging is broken off when the capacitor voltage reaches the d-c supply voltage of the d-c voltage source. If the d-c voltage source has only a small d-c voltage and/or if the load current is very large, the capacity of the quenching capacitor must be made very large, so that a charge energy sufficient for extinguishing the main valve is available. Unfortunately, having to employ such a large capacity capacitor considerably increases the cost of the converter and, thus, is quite undesirable. Moreover, a further disadvantage of such a prior art dc-to-dc converter is that the d-c output voltage derived therefrom is generally fixed at a value which is above the value of the d-c supply voltage. In some applications, however, it may be desirable to have a d-c output voltage available at the output of the converter which is of a higher or of a lower value, as desired, than the d-c supply voltage.
It is therefore an object of the present invention to develop a single-ended dc-to-dc converter whose d-c output voltage can be higher or also lower than the d-c supply voltage. Such a single-ended dc-to-dc converter would, therefore, be suited for so-called two-quadrant operation.